What is a graviton? (Intermediate)

What is a graviton? Where can it be found?

The graviton is a hypothetical particle which is thought to be responsible for carrying the force of gravity, in analogy to the photon, which is responsible for communicating all electromagnetic forces. Like a photon, it is a massless particle. However it is a spin 2 particle rather than a spin 1 particle (what is spin?).

Despite being widely accepted to exist by physicists and astronomers, direct detection of a graviton is unlikely to ever happen. Gravity is an incredibly weak force (compared to the other fundamental forces) which means that the particles that transfer it only interact very weakly with matter. As all experiments ultimately rely on interactions with matter, this means that an experiment sensitive enough to directly detect gravitons is practically impossible. However, we are able to infer information about gravitons by indirect methods, such as measuring gravitational waves. For instance, LIGO's first detection was used to estimate an upper limit on the graviton's mass of 2.1×10−58 kg.

About the Author

Mike is a fourth year astronomy graduate student at Cornell, where he works with Professors Martha Haynes and Riccardo Giovanelli on the ALFALFA survey, a blind survey of gas-rich galaxies in the local Universe carried out with the 305m Arecibo telescope in Puerto Rico.

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